cisbut2ene

Cis-2-butene, also known as cis-but-2-ene or (Z)-but-2-ene, is an alkene with the chemical formula C4H8. It is the cis isomer of but-2-ene, in which the two methyl groups attached to the double-bond carbons lie on the same side of the carbon–carbon bond. The double bond lies between the second and third carbon atoms, and the molecule is generally described as having a planar, rigid arrangement around the double bond.

Cis-2-butene is one of the geometric isomers of but-2-ene. It is an achiral molecule despite the presence of a stereochemical arrangement, and it can be distinguished from the trans isomer (trans-2-butene) by the relative positioning of the methyl groups. The (Z) notation is often used in place of cis to emphasize the same-side arrangement of substituents.

In industry, cis-2-butene occurs in hydrocarbon streams derived from petroleum refining and natural gas processing. It can be produced or enriched through refinery processes and separated from other C4 olefins by distillation and selective separation techniques. It serves as a building block in organic synthesis and can be converted into other chemical species through standard alkene reactions.

Reactions of cis-2-butene are typical of unsaturated hydrocarbons. It participates in electrophilic addition reactions such as hydrogenation (to give 2-butane), halogenation (to vicinal dihalides), and hydrohalogenation (to give substituted butanes). Hydration yields 2-butanol under acidic conditions, and the compound can also undergo polymerization under suitable catalysts.

Safety note: as a volatile hydrocarbon, cis-2-butene is flammable and may form explosive mixtures with air; handling requires appropriate precautions and ventilation.